an irish Form 11 or 12 has a section for UK pensions paid with a section then for tax deductd on that pension. If you are Irish resident and domiciled then you are taxable on your worldwide income with credit for tax paid abroad. I would think you will be taxable on this lump sum.

I am in the same position as you. I tried the Revenue office and the lady answering the phone seemed unsure. I also emailed the revenue but no reply so far. Would be interested in any further info. Is it possible to leave the lump sum in Uk and take it at a later date?